This isn't about slipping on wet tracks.
What do you do when you get delayed by a train? Do you roll to the front of the line? Hang back and wait? Take your place in line between cars?
Personally, I've found that it's a good time to take off the helmet, lean the bike against a tree or something and center myself. I take a big gulp of water, then sit down and meditate. I usually wait for traffic to pass before continuing. What do you do?